The sphenopalatine ganglion (SPG) is a complex anatomical structure involved in the genesis of various pain syndromes affecting the head and neck, typically accompanied by autonomic manifestations. Although the symptomatology may be quite variable, patients most commonly report a dull headache associated with pain in the maxillary region and teeth, together with autonomic signs such as lacrimation, rhinorrhea, and facial sweating, as well as vasomotor disturbances including conjunctival injection, facial flushing, and nasal congestion.

Headache types associated with this pathophysiology include cluster headache, paroxysmal hemicrania, SUNCT syndrome, SUNA syndrome, and Hemicrania continua. Similar mechanisms are implicated in post-dural puncture headache, post-traumatic headache, and pain syndromes following Herpes Zoster involving the ophthalmic and maxillary branches of the trigeminal nerve.^[1]

Treatment of these headache types is difficult and often insufficient. In cluster headaches, agents such as verapamil, corticosteroids, lithium medications, and anticonvulsants, including valproates and topiramate, are used. First-line medications for SUNCT include lamotrigine and topiramate. Gabapentin is considered first-line therapy for SUNA syndrome. Indomethacin is the treatment of choice for paroxysmal hemicrania and hemicrania continua. Nonsteroidal anti-inflammatory drugs are commonly used for post-traumatic and post-dural puncture headache.^[2]

In chronic cases, greater occipital nerve blocks and radiofrequency interventions targeting the sphenopalatine ganglion have proven useful.^[3] In radiofrequency (RF) procedures, temperatures reach 60–80°C for 80–90 seconds, producing ablative lesions and irreversible neurological functions. Pulsed radiofrequency (PRF), however, maintains a maximum temperature of 42°C, and tissue injury is not temperature-dependent. The principal lesional factor is the current density surrounding the electrode. PRF exerts a neuromodulatory effect without causing permanent neural damage, and its complication rate is extremely low, allowing repeat interventions.^[4] Recent literature increasingly highlights the neuromodulatory benefits of PRF for chronic pain.

The aim of the study was to evaluate the efficacy of PRF applied to the SPG in patients with chronic headache and facial pain.

This is a retrospective study with 17 patients who underwent SPG neuromodulation procedures between 2017 and 2025. The interventions were performed at the Neurosurgery Clinic of the Military Medical Academy, Sofia, and the Neurosurgery Clinic of St. Anna University Hospital, Sofia, by the same team. The mean patient age was 53±7 years (range 27–76). The cohort included 12 women and 5 men. All patients had previously undergone conservative treatment for more than 6 months without satisfactory results. Diagnoses were confirmed in consultation with neurologists and based on the diagnostic criteria of the National Consensus on the Diagnosis and Treatment of Primary Headache Types.^[5] The cohort also included three patients without trigeminal autonomic cephalgia: two with post-traumatic headache and one with post-dural (lumbar puncture) headache.

All patients were hospitalized for three days, and interventions were performed in the operating room. Preoperative antibiotic prophylaxis with 2 g IV ceftriaxone was administered two hours prior to the procedure. Patients were positioned supine with slight head extension and forehead fixation. Vital signs (blood pressure, heart rate, oxygen saturation) were continuously monitored. Mild sedation using 2.5–5 mg of midazolam or a low dose of propofol was administered while maintaining verbal contact. Fluoroscopic guidance was used for all procedures. A lateral skull projection was obtained with the C-arm centered at the mid-zygomatic arch, ensuring avoidance of overlapping images from the anterior cranial fossa and planum sphenoidale.

The sphenoid sinus and pterygomaxillary fissure were clearly visualized. After sterile preparation, the skin entry point was marked using a K-wire at the intersection of the projection line of the sphenoid sinus and the lower margin of the zygomatic arch, aligned with the fluoroscopic projection of the mandibular incisura.

A Cosman G4 (Boston Scientific) RF generator was used. A 20G SMK electrode with an active tip of 0.5 cm and a length of 3.5 inches was introduced. The dispersive electrode was placed on the abdomen ipsilateral to the intervention. Under lateral fluoroscopy, the electrode was advanced into the pterygomaxillary fissure; anterior-posterior projection confirmed placement adjacent to the lateral wall of the nasal cavity, without entering it (Fig. 1).

After C-arm verification of the position, it was advanced to sensory stimulation that confirmed the target neural structure’s proximity to the electric field of the electrode. Sensory thresholds were typically 0.4–0.6 V. Proper positioning produced paresthesia inside the nasal cavity and ipsilateral lacrimation. Paresthesia behind the incisors indicated stimulation of the maxillary division of CN V, requiring slight caudal adjustments. Paresthesia of the soft palate indicated stimulation of the greater palatine nerve, requiring posterior repositioning for a couple of millimeters.

Once verified, PRF was applied in 3 cycles with the following parameters:

– Frequency: 2 Hz

– Pulse width: 20 ms

– Interpulse interval: 480 ms

– Duration: 120 seconds

– Temperature: 42°C

– Impedance: <400 Ω

Following PRF, 2–3 mL of 0.5% bupivacaine (Marcaine Spinal) and 4 mg dexamethasone were injected through the cannula.

Pain intensity was assessed using the Visual Analog Scale (VAS) pre-procedure, on postoperative day 2, and at 3-month follow-up.^[6]

The intervention was performed on the right side in 6 patients (30%), on the left side in 9 patients (50%), and bilaterally in 2 patients (post-traumatic and post-dural puncture headache cases). All procedures were performed for chronic pain except in the post-dural puncture headache cases. The procedure was ineffective in 4 patients (≈25%), defined as VAS ≥7 at 3 months post-procedure.

A very good effect (VAS <2 and discontinuation of medications) was observed in 5 patients (30%), 3 months post-procedure.

A good effect (VAS 3–5) was recorded in 8 patients (47%), three of whom discontinued medication by month 3.

Overall, discontinuation of analgesic medication at 3 months was achieved in 8 patients (≈50% of the cases).

Two patients underwent repeat intervention after 3 months, with good subsequent outcomes.

Fig. 2 shows the declining levels of pain based on the visual analogue scale before the procedure, three days after the procedure and three months after the procedure.

In our data, in half of the cases (8 people), discontinuation of the medical treatment was achieved. The second procedure was performed in 2 patients after 3 months with good clinical results.

Table 1 shows the distribution of the patients based on efficacy and nosology.

The data demonstrates good efficacy in cluster headache, post-traumatic headache, post-dural puncture headache, and post-herpetic pain affecting V1 and V2. Moderate efficacy was observed in paroxysmal hemicrania and hemicrania continua.

PRF of the SPG is an effective and safe intervention for chronic headache and facial pain, especially in cluster headache, post-traumatic headache, and post-dural puncture headache. Limitations include the small and heterogeneous cohort, short follow-up duration, and the concurrent use of local anesthetics and corticosteroids. Future directions include diagnosis-specific studies, sham-controlled trials, and evaluation of implantable stimulation devices.